Vacuum formed bags of products such as hot dogs are sealed in a vacuum chamber so as to remove all air which could cause premature spoiling of the product. As air is removed from the bag during the vacuum forming process, the bag shrinks about the product so that the resulting package has a uniform and fixed configuration. All similarly sized packages of the same product obtain a uniform configuration after vacuum packaging. Thus the surfaces of the packages are uniformly contoured.
In some instances during a vacuum sealing process, a seal is not properly made or the package incurs a leak which allows air to enter the package. Air entering the package quickly deforms the contours that are created during the vacuum sealing process. Because there is no efficient way to detect whether a seal has been broken or a leak occurs, many products which are vacuum sealed in this manner are packaged by hand to allow an operator to inspect every package. The operator inspection method is insufficient and unreliable at full production speeds.